This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A169818 #5 Jan 03 2013 12:39:31 %S A169818 0,1,1,1,2,2,1,2,2,2,1,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,1,3,2,2, %T A169818 2,2,3,2,2,3,2,2,2,2,2,2,2,2,3,3,3,2,2,2,1,3,2,2,3,2,3,2,2,2,3,3,3,2, %U A169818 3,2,3,2,3,2,2,2,3,3,2,2,2,2,2,2,3,3,2,3,3,3,3,2,2,2,2,2,2,3,3 %N A169818 Rank of n-th prime as defined in A177854. %C A169818 This notion of rank is closely related to the Erdős-Selfridge classification of primes. %H A169818 T. D. Noe, <a href="/A169818/b169818.txt">Table of n, a(n) for n=1..10000</a> %F A169818 a(A000720(A141453(n)))=1 n>1. [From _R. J. Mathar_, May 28 2010] %t A169818 rank[1]=0; rank[2]=0; rank[3]=1; %t A169818 SetAttributes[rank,Listable]; %t A169818 rank[p_] := rank[p] = 1+Min[Max@@rank[First/@FactorInteger[p-1]], Max@@rank[First/@FactorInteger[p+1]]]; rank[Prime[Range[100]]] %Y A169818 For records see A177854. %K A169818 nonn %O A169818 1,5 %A A169818 _T. D. Noe_, May 28 2010